Class 10 > Science

Question

A convex lens has a focal length of 20 cm. Calculate at what distance from the lens should an object be placed so that it forms an image at a distance of 40cm on the other side of the lens. State the nature of the image formed?
Medium

Solution

Given: Focal length f = +20cm, Image distance v = 40cm Let u be the object distance. From lens formula. we have 1/V-1/U = 1/f On rearranging, we have 1/u - 1/v = 1/f Putting the value of respective terms. we have 1/u = 1/u - 1/40 น = -40 Hence. u=-40cm. The image is real and inverted.

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